Anomalous conductivity, Hall factor, magnetoresistance, and thermopower of accumulation layer inSrTiO3

Results of Monte Carlo simulations of electron transport for wurtzite phase GaN in crossed, weak electric and magnetic fields are presented. It is found that the Hall factor, rH = μHall/μdrift, decreases monotonically as the temperature increases from 77K to 400K.The low temperature value of the Hall factor increases significantly with increasing doping concentration. The Monte Carlo simulations take into account the electron-lattice interaction through polar optical phonon scattering, deformation potential acoustic phonon scattering (treated as an inelastic process), and piezoelectric acoustic phonon scattering. Impurity scattering due to ionized and neutral donors is also included, with the latter found to be important at low temperature due to the relatively large donor binding energy which implies considerable carrier freeze-out already at liquid nitrogen temperature. The temperature dependences of the electron concentration, drift mobility, and Hall factor are calculated for donor concentrations equal to 5 × 1016 cm−3, 1017 cm−3, and 5 × 1017 cm−3. The Monte Carlo simulations are compared to classical analytical results obtained using the relaxation-time approximation, which is found to be adequate at low temperatures and sufficiently low carrier concentrations so that inelastic scattering effects due to optical phonons and degeneracy effects are negligible. The influence of dislocations on the Hall factor is discussed briefly.

Download Full-text

More Insights Into the ZnO/a-SiC:H(B) Interface - An Improved TCO/p Contact

MRS Proceedings ◽

10.1557/proc-426-519 ◽

1996 ◽

Vol 426 ◽

Cited By ~ 14

Author(s):

E. Böhmer ◽

F. Siebke ◽

B. Rech ◽

C. Beneking ◽

H. Wagner

Keyword(s):

Fill Factor ◽

Series Resistance ◽

Depth Profiling ◽

Binding Energies ◽

Level Shift ◽

Accumulation Layer ◽

Front Electrode ◽

P Type ◽

Deposition Conditions

AbstractSolar cells based on amorphous silicon (a-Si:H) exhibit a decreased fill factor if ZnO is used as front electrode instead of SnO2. This is due to a poor electric contact between the ZnO and the p-type a-SiC:H(B) layer. To gain a deeper understanding of the chemical and electronic properties of the ZnO/p interface, in-situ XPS measurements were applied to thin a-SiC:H(B) films deposited on ZnO. The effects of CO2 and H2 plasma pretreatments on clean ZnO surfaces and the influence of deposition conditions on the ZnO/a-SiC:H interface were investigated. Upon H2 plasma treatment the formation of SiOx by chemical transport of Si from the reactor walls is observed. Furthermore, a shift of all core levels towards higher binding energies indicates the formation of an accumulation layer. CO2 plasma treatments show no effects on ZnO. Depth profiling across the ZnO/a-SiC:H interface indicates SiO2 formation on ZnO. The depth profile of ZnO related core levels exhibits two features: a reduction of the ZnO at the interface, and, after longer sputter times, a core level shift towards higher binding energy due to an hydrogen induced accumulation layer in the n-type ZnO. The latter causes a depletion of the p-layer resulting in an enhanced series resistance and diminished fill factor. To reduce the depletion layer thin highly conductive microcrystalline layers were introduced, increasing the fill factor up to 74%.

Download Full-text